The present invention relates to a new and improved construction of a press or pressing roll which is of the type comprising a non-rotatable or stationary axial support member or beam and a roll shell or jacket rotatable about the non-rotatable or stationary axial support member, supported in the direction of the non-rotatable or stationary axial support member and movably mounted in a predeterminate support or pressing direction in relation to the non-rotatable or stationary support member over the entire width or axial extent of the roll shell or jacket.
Such type of press or pressing rolls or rollers, typically referred to in the art as so-called controlled deflection rolls or rolls with bending or sag compensation, as known for instance from U.S. Pat. No. 3,885,283, granted May 27, 1975 or the cognate French Patent No. 2,205,134, serve for the pressing or pressure treatment of material webs, for instance paper-, fiber-, textile-, metal- or plastic webs.
The roll shell of the prior art press roll as known from the aforementioned U.S. Pat. No. 3,885,283, is supported by hydraulic or hydrostatic or other support elements or a pressure pad against the stationary support member or beam and in the support or pressing direction is freely movable relative to the stationary support member or beam. In this way, the roll shell of such press roll can follow a counter roll and exert a uniform line force or a desired pressure profile upon the material web which passes between the press roll and the counter roll, without being influenced by movements or sag of the counter roll. In this connection, the support elements travel upon or contact the cylindrical inner surface of the roll shell or jacket and possess a corresponding cylindrical bearing surface.
In order to prevent a displacement of the roll shell in an axial direction in relation to the support member or beam and to preclude a lateral shifting or deviation of the roll shell during operation of the press roll in a roll mill or rolling device, the roll shell of such press roll is rotatably mounted at its ends at the stationary support member by means of roller bearings upon a guide device. This guide device is movably guided in the support or pressing direction in relation to the ends of the stationary support member or beam by means of a cam guide or journal guide.
Due to the provision of the bearings at the ends of the roll shell, it is possible to fix in axial direction such roll shell. However, what is disadvantageous is that there is required a complicated design of the bearings, the PG,4 dimensions of which are dependent upon the diameter of the press roll. Additionally, there is also required a special oil for the lubrication of the bearings. Furthermore, the use of the roller bearings necessitates limiting the operating temperature. The existence of the bearings limits the rotational speed of the roll shell and during high rotational speeds of the press roll the presence of the bearings requires high power consumption of the drive. Additionally, the use of the noted cam structure produces disturbing friction in the presence of the transverse forces arising during operation of the press roll.
Furthermore, from U.S. Pat. No. 3,494,675, granted Feb. 10, 1970, there is known a controlled deflection roll, wherein both ends of the roll shell are provided with hydraulically lubricated semi-spherical cup bearings mounted upon the support member. The provision of such bearings, however, fixes the position of the ends of the roll shell in relation to the support member in a radial direction and does not afford the requisite radial mobility of the roll shell over its entire width in the support or pressing direction. Moreover, these semi-spherical cup bearings do not allow for any compensation of length variations which arise due to different thermal expansions of the roll shell and the support member as well as because of bending-through or sag of the support member during operation of the press roll. Therefore, when the press roll is in operation, a faultless bearing or mounting arrangement is not always ensured.